Posttraumatic joint contracture (PTJC) is a debilitating condition characterized by loss of joint motion following injury. Previous work in a rat model of elbow PTJC investigated disease etiology, progression, and recovery in only male animals; this study explored sex-based differences. Rat elbows were subjected to a unilateral anterior capsulotomy and lateral collateral ligament transection followed by 42 days of immobilization and 42 days of free mobilization. Grip strength and gait were collected throughout the free mobilization period while joint mechanical testing, microcomputed tomography and histological analysis were performed postmortem. Overall, few differences were seen between sexes in functional, mechanical, and morphological outcomes with PTJC being similarly debilitating in male and female animals. Functional measures of grip strength and gait showed that, while some baseline differences existed between sexes, traumatic injury produced similar deficits that remained significantly different long-term when compared to control animals. Similarly, male and female animals both had significant reductions in joint range of motion due to injury. Ectopic calcification (EC), which had not been previously evaluated in this injury model, was present in all limbs on the lateral side. Injury caused increased EC volume but did not alter mineral density regardless of sex.Furthermore, histological analysis of the anterior capsule showed minor differences between sexes for inflammation and thickness but not for other histological parameters. A quantitative understanding of sex-based differences associated with this injury model will help inform future therapeutics aimed at reducing or preventing elbow PTJC.

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Background: Simple elbow dislocation occurs at an incidence of 2.9 to 5.21 dislocations per 100,000 person-years, with as many as 62% of these patients experiencing long-term elbow joint contracture, stiffness, and/or pain. Poor outcomes and the need for secondary surgical intervention can often be prevented nonoperatively with early or immediate active mobilization and physical therapy. However, immobilization or limited mobilization may be necessary following trauma, and it is unknown how different periods of immobilization affect pathological changes in elbow joint tissue and how these changes relate to range of motion (ROM). The purpose of this study was to investigate the effects of varying the initiation of free mobilization on elbow ROM and histological features in an animal model of elbow posttraumatic joint contracture.Methods: Traumatic elbow dislocation was surgically induced unilaterally in rats. Injured forelimbs were immobilized in bandages for 3, 7, 14, or 21 days; free mobilization was then allowed until 42 days after injury. Post-mortem joint ROM testing and histological analysis were performed. One-way analysis of variance was used to compare ROM data between control and injured groups, and Pearson correlations were performed between ROM parameters and histological outcomes.Results: Longer immobilization periods resulted in greater ROM reductions. The anterior and posterior capsule showed increases in cellularity, fibroblasts, adhesions, fibrosis, and thickness, whereas the measured outcomes in cartilage were mostly unaffected. All measured histological characteristics of the capsule were negatively correlated with ROM, indicating that higher degrees of pathology corresponded with less ROM.Conclusions: Longer immobilization periods resulted in greater ROM reductions, which correlated with worse histological outcomes in the capsule in an animal model of posttraumatic elbow contracture. The subtle differences in the timing of ROM and capsule tissue changes revealed in the present study provide new insight into the distinct timelines of biomechanical changes as well as regional tissue pathology.Clinical Relevance: This study showed that beginning active mobilization 3 days after injury minimized posttraumatic joint contracture, thereby supporting an immediate-motion clinical treatment strategy (when possible). Furthermore, uninjured but pathologically altered periarticular tissues near the injury location may contribute to more severe contracture during longer immobilization periods as the disease state progresses. Simple elbow dislocation, described as a joint dislocation not involving fracture, occurs at an incidence of 2.9 to 5.21 dislocations per 100,000 person-years 1,2 . Outcomes following injury vary greatly, with as many as 62% of patients experiencing long-term elbow joint contracture, stiffness, and/or pain 2-4 . These debilitating symptoms (i.e., losses in range of motion [ROM] and joint stiffness) are collectively described as posttraumatic joint contracture (PTJC) and are due to pathol...

Background. Post-traumatic joint contracture (PTJC), characterized by loss of motion and permanent stiffness, affects up to 50% of patients following elbow joint dislocation or fracture. Mechanisms governing successful conservative treatment methods aimed at preventing elbow PTJC and avoiding operative treatments (e.g., physical therapy) are poorly understood. Using a previously established rat model of elbow PTJC, the purpose of this study was to explore the effect of varying timing, intensity and duration of active, functional exercise on joint motion outcomes. Methods. Following a surgically-induced unilateral elbow dislocation in rats, injured limbs were immobilized in bandages for 42 days followed by free mobilization for 42 additional days producing long-term PTJC. This work summarizes several studies (Phases I-III) that investigated the effects of early versus delayed therapy (timing), free mobilization versus forced treadmill walking (intensity), and limited-time versus unlimited use (duration) on elbow PTJC. Results. Joint motion outcomes in therapy groups showed no improvements compared to non-treated injured animals when therapy began day 14 post-injury or later regardless of timing, intensity or duration. Improved joint range-of-motion was only achieved when bandages were permanently removed at day 3 post-injury, regardless of whether added treadmill walking was performed. Conclusions. Early motion is essential to preserving range-of-motion following traumatic elbow injury in a rat model.

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